1. Field of the Invention
The present invention relates to a polishing apparatus and to a method of manufacturing a semiconductor device using the polishing apparatus. More specifically, the present invention relates to a polishing apparatus ensuring stable polishing characteristic, and suppressing generation of micro scratches in a step of polishing during manufacturing of a semiconductor device, as well as to a method of manufacturing a semiconductor device using the polishing apparatus.
2. Description of the Background Art
As one of the measures to meet higher degree of integration and miniaturization of semiconductor devices, a method of planarizing a surface of a semiconductor substrate by Chemical Mechanical Polishing (hereinafter referred to as "CMP method") in the manufacturing process has been known. A polishing apparatus described in Japanese Patent Laying-Open No. 8-294861 as an example of a polishing apparatus for the conventional CMP method will be described in the following.
Referring to FIGS. 21 and 22, on a rotary disk 113 rotating in a horizontal plane, a polishing cloth 115 for polishing a surface to be polished is adhered. Above rotary disk 113, a wafer holding base 114 is arranged for holding a wafer 116 such that the surface to be polished of a semiconductor substrate is opposed to the surface of polishing cloth 115. The center of rotation of wafer holding base 114 is arranged offset by a prescribed offset distance E from the center D of rotation of. rotary disk 113.
Above rotary disk 113, a polishing liquid supply tube 117 for supplying polishing liquid to polishing surface 115a of polishing cloth 115, and a dressing liquid supply tube 120 for supplying dressing liquid to polishing surface 115a are provided. Further, above rotary disk 113, a liquid draining mechanism 123 for draining waste polishing liquid and dressing liquid after polishing from polishing surface 115a is provided.
The diameter of wafer holding base 114 is shorter than the radius of rotary disk 113, and wafer holding base 114 and rotary disk 113 rotate in the directions represented by arrows A and B, respectively. In FIG. 22, a two-dotted circle F represents a track drawn near the center of rotation of polishing cloth 115 by an outer periphery of wafer 116 held by wafer holding base 114.
Main portions of the conventional polishing apparatus are structured as described above.
The operation of the polishing apparatus will be described in the following. To polishing surface 115a adhered on rotary disk 113 rotating at a constant rate, a polishing liquid containing fine alumina particles is supplied from polishing liquid supply tube 117. At the same time, dressing liquid is supplied to polishing surface 115a from dressing liquid supply tube 120. Wafer holding base 114 is moved downward while wafer holding base 114 on which a wafer 116 is fixed is rotated at a constant rate. A surface 116a to be polished of wafer 116 is pressed onto polishing surface 115a so that the surface 116a is polished. After polishing process, the waste polishing liquid and dressing liquid are recovered by liquid draining mechanism 123. In this manner, wafer 116 is polished.
The polishing process by the above described polishing apparatus, however, has the following problems. Referring to FIG. 23, part of the polishing liquid supplied from polishing liquid supply tube 117 may undesirably flow directly to a region of polishing surface 115a which goes away from wafer holding base 114 because of the disk 113 rotation, or to a region of polishing surface 115a which goes away from dressing liquid supply tube 120 because of disk 113 rotation, as represented by solid arrows. Further, part of the dressing liquid supplied from dressing liquid supply tube 120 may possibly flow directly to a region of polishing surface 115a which goes away from liquid draining mechanism 123 because of disk 113 rotation, or to a region of polishing surface 115a which goes away from polishing liquid supply tube 117 by disk 113 rotation, as represented by dotted arrows.
Further, it is possible that the waste polishing liquid after polishing directly flows to a region of polishing surface 115a which goes away from liquid draining mechanism 123 by disk 113 rotation. Accordingly, it is possible that the supplied polishing liquid and dressing liquid are mixed with each other, or polishing liquid and waste polishing liquid are mixed with each other, resulting in variation of polishing amount of the surface to be polished of the wafer, as well as in generation of micro scratches of the surface to be polished of the wafer caused by chippings.